This application relates to closure-sensitive devices and, more particularly, to devices which generate an audible or visible signal in response to the opening of a folded article.
Articles of this type have been produced in the past, especially in the field of greeting cards. Other such articles produced or at least proposed in the past include business card holders, folders, advertising and promotional literature, and product packaging, among others, as indicated in the following patents:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 4,102,067 Tarrant Jul. 25, 1978 4,299,041 Wilson Nov. 10, 1981 4,607,747 Steiner Aug. 27, 1986 4,614,266 Moorhead Sep. 30, 1986 5,275,285 Clegg Jan. 4, 1994 5,387,108 Crowell Feb. 7, 1995 ______________________________________
A common form of switch mechanism used in such articles is a slide tongue mechanism of the type disclosed in the above-referenced U.S. Pat. No. 4,607,747 to Steiner, U.S. Pat. No. 5,275,285 to Clegg, and U.S. Pat. No. 5,387,108 to Crowell. Slide tongue mechanisms have two electrical contacts biased toward each other but held apart by an insulating pull-tab or tongue. The mechanism is typically mounted with the tongue straddling a fold line in a folded article such that the tongue slides out from between the contacts enough to allow the contacts to close when the article is opened. Such mechanisms are fairly simple and inexpensive but tend to be susceptible to failure after long storage of the article in its closed position. More specifically, it is thought that the wedge force applied by the tongue can create a permanent gap between the contacts when the article is stored in its closed position, as it normally is, for a long period of time.
Light-sensitive switch mechanisms have also been proposed, such as disclosed in the above-referenced U.S. Pat. No. 4,299,041 to Wilson. However, articles employing such switch mechanisms have to be carefully designed to avoid inadvertent circuit actuation in response to ambient light.
Another prior art switch mechanism, designed for use in a business card holder, is shown in FIGS. 1 and 2. A closure-sensitive sound module 10 which includes a printed circuit (pc) board 12 and a speaker 14 is mounted on an inner surface 16 of an outer layer 18 of a double-layer panel 20 of a folding business card holder 22 which has a second double-layer panel 24 foldable with respect to panel 20 along a fold line 26. Four slots 28 are provided in an inner layer 30 of panel 24 for receiving and retaining a business card. Layers 18 and 19 of panel 20 are substantially parallel to each other and thereby together define a sleeve or thin pocket therebetween within which sound module 10 is enclosed. Circuit board 12 has a signal generator IC 32 that is powered by a button-cell battery 34 and triggered by closure of a cantilever switch 36, which includes a conductive cantilever arm 38 with a free end 40 which is exposed to contact with layer 30 via a notch 42 provided in layer 19 for this purpose. Switch 36 is normally closed but is held open by panel 24 bearing against free end 40 of cantilever arm 38 when the card holder is closed.
Cantilever arm 38 is attached at a single point 44 on the underside of the pc board and is biased upwardly toward a stationary electrical contact 46 mounted on the pc board's top surface 48. When the card holder is opened, the free end of arm 38 is released and thereby moves upwardly such that the switch closes. The IC is designed to respond to the switch closure by generating a signal which, when supplied to the speaker, produces a ringing telephone sound. Cantilever arm 38 is a leaf spring of nickel-plated spring steel having a thickness of 0.006", a width of 0.040", and a length of 3/4" from the attachment point 44 to the tip of the free end. A perpendicular tab 50 is provided on the attachment end of the arm 38, the attachment end including a rectangular plate portion shown in phantom in FIG. 2A. During assembly of the switch, the tab is inserted through a hole provided for this purpose in the pc board and then bent 90.degree. such that a portion thereof lies flush against an electrical terminal on the top surface of the board, as best shown in FIG. 2B, where it is soldered in place, e.g., with a solder bead 52 (removed from FIG. 2A for illustration purposes). Electrical contact 46 is similarly secured with a pair of solder beads 54. The cantilever arm in this switch mechanism, with its single point of attachment, has been found highly susceptible to permanent deformation upon downward flexing thereof when the card holder is closed, such that it does not reliably close as necessary upon opening the card holder after sustained closure thereof.
Thus, although folded articles with closure-sensitive signalling devices are known to be desirable and various forms thereof are functional for periods of time, there is a continuing need for greater reliability in such articles, and particularly the switch mechanisms therein, while maintaining design simplicity and low cost.